<div style="margin-top: 20px">
  测试onchanges dochek钩子
  <div>
    问候语：<input type="text" [(ngModel)]="greeting">
  </div>
  <div>
    姓名：<input type="text" [(ngModel)]="user.name">
  </div>
  <app-child [greeting]="greeting" [user]="user"></app-child>
</div>
